The invention generally relates to an arrangement of thermal shield elements for a structure carrying hot gas, especially a metallic component of a gas turbine plant or combustion chamber. The arrangement may include a plurality of thermal shield elements which are arranged next to one another on a supporting structure in such a way as to cover the surface, and which are anchored to the structure.
On account of the high temperatures prevailing in hot gas spaces, it is necessary to protect a supporting structure which is exposed to hot gas. To this end, it is possible, for example, to line the hot gas space with thermal shield elements whose surface facing the hot gas is cooled.
A thermal shield element with cooling fluid return and thermal shield arrangement for a component carrying hot gas is described in DE-U-297 14 742.0. The thermal shield component consists of a hollow arrangement with an outer shell and a small, hollow insert. Between the insert and the outer shell there is an intermediate space through which the cooling fluid can flow. The insert has passage openings for the cooling fluid on the base side. A closed-circuit cooling-fluid system is achieved by virtue of the fact that the cooling fluid flows through passages in the supporting structure into the insert, flows from there through passage openings into the outer shellxe2x80x94the cooling is effected in the process by impingement cooling and convection coolingxe2x80x94and flows back from there through separate outlet passages in the supporting structure. The multi-shell construction of the thermal shield element ensures the closed-circuit cooling-fluid system. However, such a multi-shell construction is very expensive.
A combustion chamber and a method for the steam cooling of a combustion chamber are proposed in DE 197 51 299 C2. In this case, the supporting structure of the combustion chamber consists of an inner, an intermediate and an outer wall. The cooling fluid, in particular cooling steam, flows through an inlet into an outer cooling space, flows from there through openings in the intermediate wall into an inner cooling space and flows from there to the outlet. The cooling of the inner wall is effected by impingement cooling when the cooling fluid passes over through the openings of the intermediate wall from the outer cooling space into the inner cooling space, whose wall facing the hot gas constitutes the inner wall to be cooled, and by convection cooling by the fluid flowing in the direction of the outlet. In this case, a cooling-fluid circuit is constructed by the multi-shell construction of the outer wall. Such a multi-shell construction of the combustion-chamber casing is expensive. In addition, the use of steam as cooling fluid requires the cooling steam to already be produced during the start-up of the turbine and to be fed back into the process.
An object of an embodiment of the invention is to specify a thermal shield arrangement which permits an economical operation of the plant. According to demand, an economical operation may primarily require low losses of cooling medium, low generation of noise, a high efficiency or a simple and easy-to-assemble design.
According to an embodiment of the invention, in a thermal shield element of the type specified at the beginning, a thermal shield element can be a single-shell hollow body which has a cooling-air feed passage and at least one opening for the discharge of the cooling air into a tiled intermediate space which is located between the individual thermal shield elements. Such a single-shell construction is substantially simpler in terms of design than the construction of multi-shell thermal shield elements already known.
A closed-circuit cooling-air system can be achieved in this arrangement by the cooling air flowing through the cooling-air feed passage in the supporting structure into the interior of the hollow body, where that surface of the hollow body which faces the hot gas is cooled, for example by use of an impingement-cooling plate. After the cooling air flows out into the tiled intermediate space, the air collected there can be used for the combustion.
Further minimization of the cooling-air consumption can be achieved by expansion gaps being located between the thermal shield elements, sealing elements, preferably checker metal sheets, sitting in said expansion gaps. The outflow of the cooling air from the hollow body through the at least one opening, in addition to the cooling of the lateral edges of the hollow body itself and the cooling of the adjacent thermal shield element, also ensures the cooling of the sealing element.
A thermal shield element of the arrangement can be preferably anchored under prestress to the supporting structure. Such anchoring secures the position of the thermal shield element against rotation, in particular at the hot/cold transitions often occurring during operation and during the expansion and contraction processes associated therewith of the components of the arrangement which are involved.
The sealing elements can advantageously sit in slots of the thermal shield elements, with a clearance being left in the transverse direction of the slot. As a result, adjacent thermal shield elements, after the anchoring between thermal shield element and supporting structure has been released, can be displaced relative to one another in the direction of the sealing elementsxe2x80x94i.e. in the transverse direction of the slot. A thermal shield element can be dismantled and removed from the hot gas side by releasing its anchoring to the supporting structure and that of the adjacent thermal shield elements, by pushing the adjacent thermal shield elements away from the thermal shield element to be removed, while utilizing the abovementioned clearance, and by removing the thermal shield element to be dismantled.